Antibody response to SARS-CoV-2 infection in humans: a systematic review

IntroductionProgress in characterising the humoral immune response to Severe Acute Respiratory Syndrome 2 (SARS-CoV-2) has been rapid but areas of uncertainty persist. This review comprehensively evaluated evidence describing the antibody response to SARS-CoV-2 published from 01/01/2020-26/06/2020.MethodsSystematic review. Keyword-structured searches were carried out in MEDLINE, Embase and COVID-19 Primer. Articles were independently screened on title, abstract and full text by two researchers, with arbitration of disagreements. Data were double-extracted into a pre-designed template, and studies critically appraised using a modified version of the MetaQAT tool, with resolution of disagreements by consensus. Findings were narratively synthesised.Results150 papers were included. Most studies (75%) were observational in design, and included papers were generally of moderate quality based on hospitalised patients. Few considered mild or asymptomatic infection. Antibody dynamics were well described in the acute phase, and up to around 3 months from disease onset, although inconsistencies remain concerning clinical correlates. Development of neutralising antibodies following SARS-CoV-2 infection is typical, although titres may be low. Specific and potent neutralising antibodies have been isolated from convalescent plasma. Cross reactivity but limited cross neutralisation occurs with other HCoVs. Evidence for protective immunity in vivo is limited to small, short-term animal studies, which show promising initial results in the immediate recovery phase.InterpretationPublished literature on immune responses to SARS-CoV-2 is of variable quality with considerable heterogeneity with regard to methods, study participants, outcomes measured and assays used. Antibody dynamics have been evaluated thoroughly in the acute phase but longer follow up and a comprehensive assessment of the role of demographic characteristics and disease severity is needed. The role of protective neutralising antibodies is emerging, with implications for therapeutics and vaccines. Large, cross-national cohort studies using appropriate statistical analysis and standardised serological assays and clinical classifications should be prioritised.